214 
DESCRIPTION OF THE FOSSILS. 
P. Edelburgensis. Ph. PI. VII. fig. 5. Addleburgh ; Bolland; Foun- 
tains fell. 
Semicircular, hinge line very wide, beak not prominent, deep valve evenly convex ; 
ears flattened ; both valves coarsely striated ; striae often duplicate ; spines few or none. 
Differs from P. latissima in flattened ears. 
P. latissima. Sow. PI. VIII. fig. 1. Fountains fell ; Kirby Lonsdale ; 
Otterburn, Northumberland. 
Fusiform, or convoluted ; ears conical ; striae coarse ; many small bristly spines. 
P. aurita. Ph. VII. fig. 6, 7. Ulverston. 
Hemispherical, ears prominent, rugose ; radiating striae obtuse ; spines few. Ears 
rounded in old, angular in young specimens. (I suppose this to be P. hemispherica Sow. 
but the confusion in geological works with respect to that and P. Scotica induces me 
to propose this name.) 
3 a var. j3 meniscialis. Ph. Kendal ; Queen’s County. 
Transversely elliptical, concavo-convex, no mesial hollow ; surface radiated with 
coarse round small ribs, and concentrically undulated near the beak. 
P. quincuncialis. Ph. PI. VII fig. 8. Bolland. 
Cardinal angles right, no furrow on the deep valve ; surface ridged with regular- 
strong ribs, rising alternately into oblong tubercles. 
P. scabricula. Sow. PI. VIII. fig. 2, and VIII. 20 ? Bristol ; Coalbrook- 
dale ; Bowes ; Harelaw. 
Mesial furrow broad ; numerous irregular sharp spines (or oblong tubercles) in 
quincunx, connected in lines by slight ridges from the beak of the lower valve. 
(Perhaps the large specimen figured PI. VIII. fig. 20, may be distinct ; it is from Bob. 
land.) 
P. muricata. Ph. PI. VIII. fig. 3. Harelaw ; Kirby Lonsdale. 
Back flattened ; radiating ridges rounded, continuous, strong, muricated. 
P. concinna. Sow. PI. VII. fig. 9. Richmond ; Bolland ; Derbyshire 
Semicylindrical, concave along the middle, neatly striated and spinous ; lesser valve 
flat, deeply inserted. 
P. lobata. Sow PI. VIII. fig. 7. Arran ; Otterburn, and Harelaw, 
N orthumberland. 
Distinguishable from the preceding and following, chiefly by its deeper dorsal fur- 
row, and coarser stria*. Its spines are not noticed by Sowerby. 
P. setosa. Ph. PI, V1H. fig. 9, 17. Northumberland; Rokeby. 
The length of the ears causes this to differ from P. spinosa S. to which it is other- 
wise similar- The front is uften produced into a ridge. 
